1 /*

     2  * Copyright (c) 2010, 2019, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.

     8  *

     9  * This code is distributed in the hope that it will be useful, but WITHOUT

    10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    12  * version 2 for more details (a copy is included in the LICENSE file that

    13  * accompanied this code).

    14  *

    15  * You should have received a copy of the GNU General Public License version

    16  * 2 along with this work; if not, write to the Free Software Foundation,

    17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    18  *

    19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    20  * or visit www.oracle.com if you need additional information or have any

    21  * questions.

    22  *

    23  */

    24 

    25 #ifndef SHARE_GC_CMS_PROMOTIONINFO_HPP

    26 #define SHARE_GC_CMS_PROMOTIONINFO_HPP

    27 

    28 #include "gc/cms/freeChunk.hpp"

    29 

    30 // Forward declarations

    31 class CompactibleFreeListSpace;

    32 

    33 class PromotedObject {

    34  private:

    35   enum {

    36     promoted_mask  = right_n_bits(2),   // i.e. 0x3

    37     displaced_mark = nth_bit(2),        // i.e. 0x4

    38     next_mask      = ~(right_n_bits(3)) // i.e. ~(0x7)

    39   };

    40 

    41   // Below, we want _narrow_next in the "higher" 32 bit slot,

    42   // whose position will depend on endian-ness of the platform.

    43   // This is so that there is no interference with the

    44   // cms_free_bit occupying bit position 7 (lsb == 0)

    45   // when we are using compressed oops; see FreeChunk::is_free().

    46   // We cannot move the cms_free_bit down because currently

    47   // biased locking code assumes that age bits are contiguous

    48   // with the lock bits. Even if that assumption were relaxed,

    49   // the least position we could move this bit to would be

    50   // to bit position 3, which would require 16 byte alignment.

    51   typedef struct {

    52 #ifdef VM_LITTLE_ENDIAN

    53     LP64_ONLY(narrowOop _pad;)

    54               narrowOop _narrow_next;

    55 #else

    56               narrowOop _narrow_next;

    57     LP64_ONLY(narrowOop _pad;)

    58 #endif

    59   } Data;

    60 

    61   union {

    62     intptr_t _next;

    63     Data     _data;

    64   };

    65  public:

    66   PromotedObject* next() const;

    67   void setNext(PromotedObject* x);

    68   inline void setPromotedMark() {

    69     _next |= promoted_mask;

    70     assert(!((FreeChunk*)this)->is_free(), "Error");

    71   }

    72   inline bool hasPromotedMark() const {

    73     assert(!((FreeChunk*)this)->is_free(), "Error");

    74     return (_next & promoted_mask) == promoted_mask;

    75   }

    76   inline void setDisplacedMark() {

    77     _next |= displaced_mark;

    78     assert(!((FreeChunk*)this)->is_free(), "Error");

    79   }

    80   inline bool hasDisplacedMark() const {

    81     assert(!((FreeChunk*)this)->is_free(), "Error");

    82     return (_next & displaced_mark) != 0;

    83   }

    84   inline void clear_next()        {

    85     _next = 0;

    86     assert(!((FreeChunk*)this)->is_free(), "Error");

    87   }

    88   debug_only(void *next_addr() { return (void *) &_next; })

    89 };

    90 

    91 class SpoolBlock: public FreeChunk {

    92   friend class PromotionInfo;

    93  protected:

    94   SpoolBlock*  nextSpoolBlock;

    95   size_t       bufferSize;        // number of usable words in this block

    96   markWord*    displacedHdr;      // the displaced headers start here

    97 

    98   // Note about bufferSize: it denotes the number of entries available plus 1;

    99   // legal indices range from 1 through BufferSize - 1.  See the verification

   100   // code verify() that counts the number of displaced headers spooled.

   101   size_t computeBufferSize() {

   102     return (size() * sizeof(HeapWord) - sizeof(*this)) / sizeof(markWord);

   103   }

   104 

   105  public:

   106   void init() {

   107     bufferSize = computeBufferSize();

   108     displacedHdr = (markWord*)&displacedHdr;

   109     nextSpoolBlock = NULL;

   110   }

   111 

   112   void print_on(outputStream* st) const;

   113   void print() const { print_on(tty); }

   114 };

   115 

   116 class PromotionInfo {

   117   bool            _tracking;      // set if tracking

   118   CompactibleFreeListSpace* _space; // the space to which this belongs

   119   PromotedObject* _promoHead;     // head of list of promoted objects

   120   PromotedObject* _promoTail;     // tail of list of promoted objects

   121   SpoolBlock*     _spoolHead;     // first spooling block

   122   SpoolBlock*     _spoolTail;     // last  non-full spooling block or null

   123   SpoolBlock*     _splice_point;  // when _spoolTail is null, holds list tail

   124   SpoolBlock*     _spareSpool;    // free spool buffer

   125   size_t          _firstIndex;    // first active index in

   126                                   // first spooling block (_spoolHead)

   127   size_t          _nextIndex;     // last active index + 1 in last

   128                                   // spooling block (_spoolTail)

   129  private:

   130   // ensure that spooling space exists; return true if there is spooling space

   131   bool ensure_spooling_space_work();

   132 

   133  public:

   134   PromotionInfo() :

   135     _tracking(0), _space(NULL),

   136     _promoHead(NULL), _promoTail(NULL),

   137     _spoolHead(NULL), _spoolTail(NULL),

   138     _spareSpool(NULL), _firstIndex(1),

   139     _nextIndex(1) {}

   140 

   141   bool noPromotions() const {

   142     assert(_promoHead != NULL || _promoTail == NULL, "list inconsistency");

   143     return _promoHead == NULL;

   144   }

   145   void startTrackingPromotions();

   146   void stopTrackingPromotions();

   147   bool tracking() const          { return _tracking;  }

   148   void track(PromotedObject* trackOop);      // keep track of a promoted oop

   149   // The following variant must be used when trackOop is not fully

   150   // initialized and has a NULL klass:

   151   void track(PromotedObject* trackOop, Klass* klassOfOop); // keep track of a promoted oop

   152   void setSpace(CompactibleFreeListSpace* sp) { _space = sp; }

   153   CompactibleFreeListSpace* space() const     { return _space; }

   154   markWord nextDisplacedHeader(); // get next header & forward spool pointer

   155   void    saveDisplacedHeader(markWord hdr);

   156                                  // save header and forward spool

   157 

   158   inline size_t refillSize() const;

   159 

   160   SpoolBlock* getSpoolBlock();   // return a free spooling block

   161   inline bool has_spooling_space() {

   162     return _spoolTail != NULL && _spoolTail->bufferSize > _nextIndex;

   163   }

   164   // ensure that spooling space exists

   165   bool ensure_spooling_space() {

   166     return has_spooling_space() || ensure_spooling_space_work();

   167   }

   168 

   169   template <typename OopClosureType>

   170   void promoted_oops_iterate(OopClosureType* cl);

   171 

   172   void verify()  const;

   173   void reset() {

   174     _promoHead = NULL;

   175     _promoTail = NULL;

   176     _spoolHead = NULL;

   177     _spoolTail = NULL;

   178     _spareSpool = NULL;

   179     _firstIndex = 0;

   180     _nextIndex = 0;

   181 

   182   }

   183 

   184   void print_on(outputStream* st) const;

   185 };

   186 

   187 

   188 #endif // SHARE_GC_CMS_PROMOTIONINFO_HPP